This Program Project Grant has as its theme epidemiologic research on diet and cancer in the multiethnic population of Hawaii. It brings together two aspects of our current research: studies on the role of diet in cancer etiology, and studies of dietary methodology in epidemiologic research. Seven separate but interrelated projects and proposed. Four of these are etiologic studies of cancer (including colon, breast, thyroid, lung, bladder and others) in relation to dietary exposures to specific foods and their nutrient components (such as fats, cholesterol and vitamins). These four studies involve both cohort and case-control approaches, and build on the results of our earlier cross-sectional and case-control studies. Data collection primarily involves personal interviews and surveillance, although biological specimens will also be collected in one of the studies. Three other studies examine different aspects of the diet history method, including its validity, its reproducibility, and the equivalence of different methods for quantifying dietary intakes. All seven projects entail considerable overlap in professional and technical personnel, as well as in the use of core support components. This research program should not only advance our knowledge about the role of dietary factors in the etiology of cancer, but also lead to better dietary history data collection methods for future epidemiological studies.